1. Field of the Invention
This invention relates to sheet piling devices and particularly to such devices which have: carrier elements for the pile, which carrier elements can be driven towards the pile and in the direction of sheet transport by means of a drive; a pile removal device; and, a separating device which can be introduced at the pile front edge in order to separate one pile from the next.
2. Prior Art
Such piling devices are known, for example from U.S. Pat. No. 2,205,767. In the device there described individual sheets which are transported by means of a belt are laid down to form a pile which is formed on a sinking pile table, the surface of which is constituted by a pile removal device in the form of a conveyor belt. Prior to pile removal, carrier elements are introduced in the sheet transport direction between the pile and the incoming sheets, so that a new pile forms on the carrier elements while the remaining pile is lowered and transported away. After the pile table has been raised again, the pile which has formed in the meantime on the carrier elements is again put onto the main pile table and the carrier elements guided again into their starting position below the sheet transport path. With this device, however, difficulties arise in the introduction of the carrier elements between the pile and the subsequent sheets if the piling device is to operate with a high sheet frequency.
A piling device has become known from German Auslegeschrift No. 1303445 in which, in order to change the pile, a separating device is provided in the form of a separating shoe which can be swung in at the front edge of the pile, onto which the front edges of subsequent sheets run while the pile formed thereunder is pulled away by grippers in the sheet transport direction. With high working speeds and particularly high pile heights, however, difficulties can arise here also if the newly formed pile, after pulling away the old pile, falls down with its rear edge onto the pile table. The exact alignment of the pile can be lost as a result.
From German Auslegeschrift No. 1230810 a piling device of the initially described type is known in which the carrier elements, which can be guided in the sheet transport direction, are provided with blowing air openings at their front end in order to facilitate the introduction of the carrier elements. Even this device brings substantially no improvement with large format sheets and high working speeds.
A piling device for plate-like articles is known from U.S. Pat. No. 3,606,310 in which each individual plate is taken from the feed conveyor by carrier elements which move in the piling region in the fashion of a paternoster, i.e. first horizontally and then vertically in order to lower the plates until just above the pile and then they pull back again horizontally. Such a device is unsuitable for paper sheets and particularly for high working speeds. It is also not possible with this arrangement to pile an overlapped incoming stream of sheets.
Since with customary piling devices it is possible to form very high piles, often high piles are formed by laying on top of one another several low part-piles. In order to do this not only is a special device necessary, but there is also the danger that the part-piles will tip over while being laid on top of one another. Additionally, in the finished pile, the separation positions between the original part-piles are generally evident.